Since the discovery of carbon nanotubes in 1991, interest has focused on exploiting their novel electronic and mechanical properties on a macroscopic scale in polymer composites (Iijima, S., Nature (1991)). For example, nonlinear optical (NLO) properties of nanotube composites have applications in optical sensor technology (Jin, Z. et al., Chem. Phys. Lettrs. (2000)). Nanotubes are also of great interest in electromagnetic (EMI) shielding applications and in the design and development of nanoscale electronic devices (see Grimes, C. A. et al., Chem. Phys. Lettrs. (2000); and Star, A. et al., Agnew. Chem. Int. Ed. (2001)). Their high aspect ratio, mechanical strength and high modulus have prompted scientists to design and characterize novel composites of carbon nanotubes embedded in a series of host polymers (see Shadier, L. S. et al., Apply. Phys. Lettrs. (1998); Qian, D. et al., Apply. Phys. Lettrs. (2000); Bower, C. et al., Apply. Phys. Lettrs. (1999); Jin, L. et al., Apply. Phys. Lettrs. (1998); and Lourie, O. and H. D. Wagner, Apply. Phys. Lettrs. (1998)). Such ultra-strong, low-density, carbon nanotube composites demonstrate extraordinary potential for structural design in the building and automotive industry.
The chemical modification of nanotubes further broadens their uses in polymeric composites. Experimental results indicate that certain free-radical initiators open TC bonds in carbon nanotubes. Indeed, when present during the addition polymerization of methyl methacrylate to create polymethylmethacrylate (PMMA), carbon nanotubes have been shown to participate in the polymerization process (Jia, Z. et al., Mater. Sci. and Eng. (1999)). Several studies show that electron and ion beam irradiation of nanotubes gives rise to amorphization and dimensional changes. In some instances, irradiation appears to be responsible for “soldering” nanotubes to form mechanical junctions (see Banhart, F., Nano Lettrs. (2001); Krasheninnikov, A. V. et al., Phys. Rev. (2001); Kiang, K. H. et al., J. Phys. Chem. (1996); McCarthy, B. et al., J. Mater. Sci. Letter. (2000); and Hwang, G. L. and K. C. Hwang, Nano Lett. (2001)). Untrasonification has been used to induce the sonochemical reactions of single wall carbon nanotubes (SWNTs) and organic materials (Koshio, A. et al., Nano Lettrs. (2001)). Further intensive investigations document the functionalizing of nanotubes to render them soluble in various polymeric and liquid media (see Niyogi, S. et al., J. Amer. Chem. Soc. (2001); Hamon, M. A. et al., Adv. Mater. (1999); Sun, Y. et al., J. Amer. Chem. Soc. (2001); and Satishkumar, B. C. et al., J. Phys. B. At. Mol. Opt. Phys. (1996)).
These previous studies prompted an investigation of the effects of gamma radiation on PMMA/SWNT nanocomposites. This study subjected irradiated samples of PMMA/SWNT composites to thermal and mechanical testing. Scanning electron microscopy (SEM) was employed in order to document radiation-induced effects on the nanocomposite structure.
All references cited herein are incorporated by reference in their entirety, to the extent not inconsistent with the explicit teachings set forth herein.